1. Field of Invention
This invention relates generally to preparations for promoting sound oral hygiene, and more particularly to a storable, normally inactive composition which when applied onto the surface of teeth and adjacent gum tissues is then activated to carry out two functions, the first being cosmetic which is to whiten and brighten the teeth, the second being therapeutic which is to combat dental plaque and the resultant periodontal disease.
2. Status of Prior Art
In good part, the incidence of dental caries and periodontal disease can be imputed to the formation of plaque on the teeth. It has been reported in the literature that most of the world's population suffers from periodontal disease which is largely responsible for the loss of teeth.
Dental plaque is constituted by a thin layer of mucilaginous film which is subject to invasion by colonizing bacteria. Metabolic activity of these bacteria in the presence of dietary carbohydrates leads to the production of acetic and other acids. These acids attack soft gum tissue, thereby causing gingivitis; that is, the reddening and swelling of the normally pink guns, often accompanied by bleeding. These acids also react with the calcium of the teeth and the resultant decalcification of the organic matrix or dentin is such as to allow for the further invasion of bacteria and liquefying enzymes. Hence vital to sound oral hygiene is the reduction and control of dental plaque.
As noted in the Ng et al. U.S. Pat. No. 4,839,156 (1989), it has long been recognized that peroxy compounds such as hydrogen peroxide are effective against dental plaque, gingivitis, periodontitis and traumatic oral lesions. Hydrogen peroxide mouth rinses and other preparations inhibit the colonization and multiplication of the anerobic bacteria associated with dental plaque and periodontal disease. And because hydrogen peroxide functions as a bleaching agent, it will also act to whiten stained or discolored teeth, or normal teeth whose hard enamel surface has a somewhat yellowish or grayish tinge.
Most peroxy compounds tend to be unstable in storage, either because they are incompatible with other common ingredients included in the oral hygiene composition, or because they react with these ingredients. As a consequence, the composition loses its capacity to release active or nascent oxygen to attack the anerobic bacteria colonizing the plaque. To overcome this drawback, the Ng et al. patent provides a stable, aqueous, hydrogen peroxide gel.
Also concerned with the stability of hydrogen peroxide is the Winston et al. U.S. Pat. No. 4,812,308 (1989). To create a stable composition, this patent provides a tooth powder which is a mixture of sodium bicarbonate and sodium percarbonate. When this powder mixture makes contact with water, it releases active hydrogen peroxide.
Another approach to providing a stable hydrogen peroxide to combat periodontal disease is that taken in the Schaeffer U.S. Pat. No. 4,525,180 (1985) in which a hydrogen peroxide gel is stored in one compartment of a collapsible squeeze tube. Stored in the other compartment is a sodium bicarbonate paste which makes contact with the hydrogen peroxide gel only when the tube is squeezed.
The Clipper et al. U.S. Pat. No. 4,537,778 (1985) discloses an oral hygiene preparation in which hydrogen peroxide is combined with other ingredients with which this peroxide is compatible.
The Scheller U.S. Pat. No. 4,223,003 (1980) discloses a dentifrice which may be in paste or powder form and includes magnesium peroxide as an oxidizing agent for removing film from teeth. And the Smigel U.S. Pat. No. 4,405,559 (1982) discloses a dental paste that includes calcium peroxide and sodium perborate as oxidizing agents to remove stain and plaque from the teeth.
The use of hydrogen peroxide as an oxidizing agent to fight plaque and to remove stains present problems, for hydrogen peroxide is not only unstable and can quickly lose its efficacy, but it is also not free from toxicity and therefore may have adverse side effects if the dosage is excessive or its use is unduly prolonged. This is also true of other peroxy compounds such as sodium perborate.
Because a composition in accordance with the invention includes magnesium peroxide, the above-cited Clipper patent is of particular interest, for this 1985 patent indicates that it is known to use magnesium peroxide in an oral composition for prophylactic treatment with respect to caries, dental plaque, gingivitis and tooth stains. However, Clipper points out that magnesium peroxide "tends to be unstable in storage, continuously losing the capacity to release active nascent oxygen over relatively short periods of time." Clipper's preparation which has "enhanced stability in storage" includes hydrogen peroxide as the source of active oxygen. But for the reasons previously given, not only is hydrogen peroxide somewhat unstable, but it is not free from toxicity; hence a preparation of the Clipper type may have adverse effects.